Here is a suggested method to create a turnout with rails in 3D when the turnout is in a curve with cant.
The same method applies as well for external bending.
External bending can result in negative cant in the turnout branch.
Actually it can be addressed by using Force Positive (instead of Inside Rail) + negative cant in the cant created for the turnout branch.
In the following example I have 2 left hand radius with negative cant (also crazy value just to emphasize the effect), then the turnout ends with the right hand radius of the main line (3 radius in the turnout).
I am using Force Positive only for the highlighted turnout cant. You can see that cant is well applied using diagram and left/right rail value.
In this particular case, I found an issue with 3D rails orientation. There is a wrong variation of the angle corresponding to a "variation' from -126mm to 126mm along the second arc.
In fact there is no real variation, it is just because of negative vs positive cant.
I minimized this bad effect by adding a cant point just before the last arc.